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What to watch for as results come

6 p.m.

IN*, KY** = part of state closes later

Mitt Romney’s margin of victory in Indiana, which Barack Obama won in 2008, could serve as a barometer for the rest of the election. A double-digit win will warm Republican hearts. Networks will be offering exit polls, but be wary. They have an uneven record in predicting winners of states. In 2004, early exit polls in Ohio showed John Kerry to be winning, but the state went to President Bush. Also, the time between the closing of polls and the declaration of a winner of that state can vary widely according to such factors as how many votes were cast early and the closeness of the race. Early votes are counted right after polls close.

Even though this has been a historically tight race, it’s possible the night could end early because most of the tossup states close by 8 p.m. and a candidate sweep here could determine the winner. “I’d be surprised if it was tipped early,” said Robert Alexander, chairman of the Department of History, Politics and Justice at Ohio Northern University and an Electoral College expert. “But if these battleground states that close early go for Obama — Virginia, North Carolina, Florida, Pennsylvania — then I think that would spell pretty big trouble for Romney.” Conversely, an upset win for Romney in the Keystone State would boost the GOP ticket’s chances on the electoral map and indicate broader-than-expected support for Romney. The most likely state to tip the election remains Ohio. “Ohio is key,’’ Alexander said. “It’s always been a very strong bellwether state. No Republican’s won the White House without Ohio.”

The key state here is Florida, the focal point of the disputed 2000 election. Romney is slightly favored. Early voting has been extremely heavy and chaotic. Also, New Hampshire has only 4 electoral votes but could play big if the other tossup states are split. This will also be the time to check in on the Senate race between Scott Brown and Elizabeth Warren.

Polls in most swing states will have closed, but if the election remains tight, the red state of Nebraska could become important because it and Maine are the only two states that award some electoral votes by congressional district. Four years ago, Obama picked up one electoral vote in Nebraska by winning Omaha. Also, Colorado, traditionally Republican until Obama won it in 2008, will be closely watched.

10 p.m.

IA, ID*, MT, NV, OR*, UT

Iowa and Nevada are the last two states whose outcomes are in doubt, though Nevada has broken for Obama in recent polling and the president holds an advantage in early voting. If Romney were to lose Ohio but win most of the other battleground states in the East, he could take an improbable path to the White House with a victory in Iowa or a comeback in Nevada.

11 p.m. CA, ID, OR, WA

Midnight AK, HI

Beyond

In the case of an Electoral College tie, the House would pick the president, and the Senate would select the vice president. There’s also a chance that a critical state, like Ohio, will remain too close to call without counting provisional ballots, which begins on Nov. 17.

Key Senate races outside Massachusetts

Virginia

The country’s most expensive race is a battle of the titans, with former governors Tim Kaine and George Allen vying for an open seat, one of about a dozen that will determine control of the chamber. An interesting dynamic at play here is ticket splitting. Republican Mitt Romney leads in the polls — but so does Kaine, a Democrat.

Indiana and Missouri

Call these races double trouble for the GOP. Comments about rape and abortion sparked uproars. Indiana Treasurer Richard Mourdock had hoped to ride Tea Party fervor to victory, as he did in the primary against longtime incumbent Richard Lugar. In Missouri, Senator Claire McCaskill was thought to be the most endangered Democrat but now leads Representative Todd Akin.

Connecticut

Linda McMahon, the former pro wrestling executive, is making another run for Senate. Two years ago, she spent about $50 million of her personal wealth to finance a campaign that lost by 12 percentage points. She’s again dumping another $50 million into her second bid – but recent polls show her trailing Representative Chris Murphy.

Wisconsin

Democrats were hoping for a Tea Party opponent to boost the chances of Representative Tammy Baldwin. Instead, she got moderate former governor Tommy Thompson, who opened a sizable lead in early polls. But Baldwin, who would be the Senate’s first openly gay member, rebounded. Will the presence of native son Paul Ryan, the GOP veep nominee, help Thompson?

Key House races

New Hampshire

Republicans Frank Guinta and Charlie Bass are looking to hold on to the state’s two congressional seats, in a pair of rematches from two years ago. Carol Shea-Porter wants her District 1 seat back from Guinta; Ann Kuster is hoping to even the score with Bass, who won by fewer than 4,000 votes.

Florida

Representative Allen West, a Tea Party favorite, has described his opponent, Patrick Murphy, as a spoiled brat. Democrats have bashed West for asserting that “78 to 81” Democratic House members were card-carrying communists. A West loss could be viewed as a Tea Party blowback.

California

Only in California. Representatives Brad Sherman and Howard Berman — both Democrats — came close to fisticuffs during a debate last month. Redistricting and an open primary that advances the top two finishers, regardless of party, caused these two California heavyweights to collide.

Correction: Because of a designer’s error, an electoral map that was attached to this election watcher’s guide was outdated. To see how many electoral votes each state has, check the graphic here.

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